Assets Measured at Fair Value on Non-Recurring Basis (Detail) (Fair Value, Measurements, Non-Recurring [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	$ 13,759	$ 15,825
Impaired loans [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	13,621	15,496
Other real estate owned [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	138	329
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Impaired loans [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other real estate owned [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	0
Significant Other Observable Inputs (Level 2) [Member] | Impaired loans [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	0
Significant Other Observable Inputs (Level 2) [Member] | Other real estate owned [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	13,759	15,825
Significant Unobservable Inputs (Level 3) [Member] | Impaired loans [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	13,621	15,496
Significant Unobservable Inputs (Level 3) [Member] | Other real estate owned [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	138	329
Total Gains (Losses) Recognized [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	632	(2,621)
Total Gains (Losses) Recognized [Member] | Impaired loans [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	632	(2,496)
Total Gains (Losses) Recognized [Member] | Other real estate owned [Member]
Fair Value Of Assets And Liabilities Measured At Non Recurring Basis [Line Items]
Assets measured at fair value	$ 0	$ (125)